Prior Art
A device according to this generic type is known from EP 0 868 619 B1. The device diagrammed in FIG. 6 and explained briefly in the attached description is in fact not subject matter of the patent claims of this publication, however the features disclosed prove how through simple modification to the protected actuating device 1 (reference numbers of the figures therein) a double seat valve can be activated, whose independently actuated first closing element 4 is designed as a sliding piston with radial sealant and whose dependently actuated second closing element 5 is designed as a seat disc. In this closing element configuration the partially open position T1 of the first closing element 4 is completed in the opposite direction to the opening stroke H, which is directed upwards relative to the diagrammed position of the valve. For execution of the partially open position T1 a main piston 106 of the main adjustment device 1a is loaded from above with pressurizing medium D2 using a non-specified pressurizing medium connection. The partial stroke limit downwards of the first closing element 4 occurs in that a valve stem 104 takes its bearing on the latter through a non-specified recess above a spring abutment 119. The partially open position T2 of the attached actuated second closing element 5, which only has a freedom of motion upwards due to its design as a seat disc, is done using a piston 108, which is loaded with pressurizing medium D3 using a first pressurizing medium connection 117. The synchronization of a hollow bar 105 connected with the second closing element 5 upwards is done using its hollow bar head 105a. The partial stroke limit of the piston 108 is implemented through a second recess 114a on the stop sleeve 114.
The preceding briefly described actuator is also designated in expert circles as a so-called “integrated” actuator, because it accommodates the main adjustment device 1a for the full opening stroke H as well as the individual adjustment devices 1b, 1c for the partially open positions T1 and T2 in a common housing. These types of actuators are as a rule compactly built and make it possible to arrange a so-called control module and/or control head 8 (FIG. 1) directly above the main adjustment device 1a, if the individual adjustment devices 1b, 1c are arranged in the previously described manner in reference to the main adjustment device 1a. 
The significant disadvantages of the integrated actuators arise also from the fact that they are designed for the maximum requirements which are placed on double seat valves of the type under discussion. Maximum requirements are then given if, along with the full opening stroke H which is executed by the main adjustment device, the opposed partially open positions T1, T2 of both closing elements for the execution of the respective seat cleaning, which is carried out by an individual adjustment device assigned to each closing element to be activated, are necessary. Since a large portion of the double seat valves placed in installations in the food and beverage industry are in applications without the possibility or necessity of seat cleaning, because only mixing efficiency is required, integrated actuators in which only the main adjustment device is activated are normally too complex and therefore uneconomical. In practice these types of applications then fall back on “normal” actuators (standard actuators) for double seat valves, which only accommodate a main adjustment device for the full open position H. Thereby the number of integrated actuators from a manufacturer of double seat valves is reduced, since each double seat valve corresponding to the requested requirements is at best equipped with a suitable actuator for this purpose and thereby results in an uneconomical number of manufactured integrated actuators as the case may be.
A further integrated actuator for a double seat valve according to this generic type is known from the EP 1 030 988 B1. The kinematics of this actuator corresponds in an identical manner to that according to FIG. 6 in the EP 0 868 619 B1. In contrast to the latter, in the former the partial stroke movement T1 opposed to the full opening movement H of the independently actuated first closing element which is designed as a sliding piston is executed by a separate third working piston 30, which is arranged above the first working piston 18, which causes the full opening stroke H. The general arrangement is therefore in fact more complex, however by the separate third pressure chamber 39 created over the third working piston 30 the necessary volume for its loading with pressurizing medium is significantly reduced compared to the corresponding pressure chamber over the main piston in actuation of the double seat valve according to EP 0 868 619 B1, whereby less pressurizing medium is used when switching the assigned partial stroke movement T1 and the actuation reacts quicker to the switching command in this regard. At the same time the integrated actuator according to EP 1 030 988 B1 is in turn also relatively complexly constructed and flawed with the preceding briefly presented further disadvantages in connection with the integrated actuator according to EP 0 868 619 B1.
In DE 31 33 273 C2 it was already proposed for a cleanable double seat valve with leakage control, to additively insert the individual adjustment devices between the main adjustment device and a lantern housing under the main adjustment device which exclusively creates the full stroke for the full open position as the only adjustment device without changing the neighboring standard member. However it is concerned here with a double seat valve, which has two closing elements designed as seat discs, so that the full stroke H for the full open position and both partial stroke movements T1, T2 are aligned for gapwise removal of the closing elements from their respective seat surfaces. These attainable advantages with this so-called “modular” actuator concept especially exist in that to the greatest possible extent a standardized double seat valve, which has available a standard actuator for the creation of the fully open position through additive of relatively simple individual adjustment devices, contains special functions in regards to the previously described creation of partially open positions of both closing elements. From DE 31 33 273 C2 there are no details to be taken on whether the known modular actuator concept is applicable to double seat valves of the preliminary characterized type and not at all what this type of solution could look like.
The dependently actuated closing element of the double seat valve, which is also designated as a double disk with its two seals, is in fact not critical during the seat cleaning in regards to its partially open position T2 and can therefore be moved against a fixed stop for the execution of the aligned seat cleaning position. This stop therefore needs no complex pre-adjustment or readjustment. During the seat cleaning the cleaning solution is normally under pressure on the dependently actuated closing element, so that this must be opened by the partial stroke T2 against the resulting closing force from the corresponding pressure and the assigned effective surface of this closing element. To overcome this closing force or holding down force the assigned second individual adjustment device is to be dimensioned accordingly. Either a sufficiently large piston surface of the actuating piston in this second individual adjustment device is to be provided or the pressure of the pressurizing medium loaded on the actuating piston is to be correspondingly increased if there are restrictions in regards to the dimension of the diameter of the actuating piston. An adjustment of the actuator to the existing pressure conditions using a corresponding dimensioning of the actuating piston is always primarily a question of cost and is normally only chosen if other possibilities are not available. The choice of a higher pressure of the pressurizing medium is normally preferred; it is however always eliminated in practice if the installation or plant in which the cleanable double seat valve is installed does not have a pressure level available in this regard or out of cost considerations can not be additionally done.
It is the object of the present invention to design a device according to this generic type in such a manner that it is constructed as simply as possible and is easily and economically adjustable to the various requirements which are put onto a double seat valve of the type in discussion (only full opening stroke or full opening stroke as well as seat cleaning partial strokes).
Furthermore in the scope of an advantageous embodiment of the proposed device a larger flexibility should be ensured in the adjustment of the second individual adjustment device for the partial stroke movement of the dependently actuated closing element on the available pressure of the pressurized medium.